Handle JSON format requests in error responses

- Add proper format handling to RedirectsController#catch_all
- Explicitly handle JSON format in ApplicationController#not_found
- Return 404 status without template for non-HTML requests
- Fixes errors for requests like .well-known/assetlinks.json

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: Shpigford

app/controllers/application_controller.rb

@@ -25,6 +25,7 @@ def not_found
           render file: Rails.root.join("public", "404.html"), status: :not_found, layout: false
         end
       end
+      format.json { head :not_found }
       format.any { head :not_found }
     end
   end

app/controllers/redirects_controller.rb

@@ -8,10 +8,16 @@ def catch_all
       destination = redirect_rule.process_destination(request.path)
       redirect_to destination, status: redirect_rule.status_code
     else
-      if Rails.env.production? || Rails.env.development?
-        render "errors/not_found", status: :not_found
-      else
-        render file: Rails.root.join("public", "404.html"), status: :not_found, layout: false
+      respond_to do |format|
+        format.html do
+          if Rails.env.production? || Rails.env.development?
+            render "errors/not_found", status: :not_found
+          else
+            render file: Rails.root.join("public", "404.html"), status: :not_found, layout: false
+          end
+        end
+        format.json { head :not_found }
+        format.any { head :not_found }
       end
     end
   end